The nanostructure and dynamic mechanical properties of polyvinyl chloride (PVC) and the bentonite nanocomposites have been investigated. Nanocomposites with 5 wt% concentration of bentonite were prepared by melt extrusion followed by two‐roll‐milled processing. Atomic force microscopy (AFM) and wide‐angle X‐ray scattering (WAXS) were utilized to study the micro and nanostructure of the two‐roll‐milled sheets. The nanocomposites were compounded with two types of coupling agents: KZTPP® and Tamol 2001®. Optical microscopy showed that the materials remained optically transparent, i.e. they did not show evidence of nanoclay agglomeration. The WAXS patterns of PVC‐bentonite‐KZTPP nanocomposite were anisotropic, suggesting flow‐induced preferred orientation of the nanoplates. Moreover, the 001 reflection of the bentonite was shifted toward smaller angles, suggesting that the nanoplates were intercalated by the macromolecules. On the other hand, the WAXS patterns of PVC‐bentonite‐Tamol 2001 nanocomposite remained isotropic and did not show evidence of bentonite, suggesting exfoliation of the nanoplates. The nanocomposites showed an increase in glass transition temperature Tg, with the sequence Tg,PVC < Tg,KZTPP < Tg,Tamol 2001. Moreover, dynamic mechanical analysis (DMA) showed an increase in mechanical moduli and activation energy (and a decrease in the intensity of the mechanical damping Tan δ) following the same sequence. Interestingly, the improvement in mechanical moduli became more pronounced above the glass transition temperature. Copyright © 2008 John Wiley & Sons, Ltd.

SYNOPSISBinary blends of poly(viny1 alcohol) (PVA) with poly( acrylic acid) (PAA) and polyacrylamide ( PAAm) were characterized by differential scanning calorimetry (DSC) , thermal gravimetric analysis (TGA) , and infrared spectroscopy ( IR) . Molecular weight, blend composition, and heating time at 150°C were the variables used. Results obtained by DSC indicated that PAA/PVA blends are miscible in the full range of composition. Similarly, TGA traces showed that thermal stability was higher for blends than for pure polymers. Blends of PVA with high molecular weight PAA exhibited a hydrogel behavior after drying at relatively low temperature ( 100°C), whereas blends containing low molecular weight PAA behaved as hydrogels only after they were heated at 150°C. Hydrogel character was increased for these two PVA/PAA blends with the heating time a t higher temperature ( 150°C). IR spectra revealed that esterification took place in these blends after thermally treated at this temperature. In contrast, addition of glyoxal in combination with heating was necessary to produce hydrogels from PAAm/ PVA blends. Furthermore, the crosslinking degree of these hydrogels was estimated from their absorbency values by applying the Flory-Rehner equation. 0 1993 John Wiley & Sons, Inc.

SYNOPSISBinary blends of poly (caprolactone) (PCL) with cellulosic esters [cellulose diacetate (CDA) , cellulose acetate-butyrate (CAB), and cellulose triacetate (CTA) ] were studied by using differential scanning calorimetry (DSC ) , dynamic mechanical analysis (DMA) , and wide-angle X-ray scattering ( WAXS ) techniques, and qualitative comparison was made with the results obtained by polarizing optical microscopy. The PCL-CAB system was proved to be partially miscible, whereas PCL-CDA and PCL-CTA appeared to be immiscible. A double-melting behavior was showed for PCL-CAB and PCL-CTA blends. As these peaks did not shift by varying the heating rate of DSC runs, this behavior can be due to melting of two populations of crystals of PCL, which may be different in size. On the other hand, blends of PCL containing a low amount of CAB or CDA seem to develop more crystallinity for the PCL than this polymer alone. The solvent seems to have a certain influence on the thermal and morphological behaviors of the as-cast blends of these three systems, affecting the extent of crystallinity of PCL, as well as its T,,, and AH,. This finding is discussed in the light of WAXS and polarizing optical microscopy results. 0 1994 John Wiley & Sons, Inc.

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SYNOPSISThe physical properties, thermal stability, and interaction with liquids of cellulosic fibers isolated from henequen fibers (Agaue fourcroydes) by an alkaline digestion process were determined. Physical dimensions, apparent length, and diameter of henequen cellulosic fibers were determined by optical microscopy in a random sample of 125 fibers. Other properties such as crystallinity, specific gravity, and cellulose type were also determined. The sorption of several liquids in these cellulosic fibers was measured and correlated to the polar and hydrogen bonding components of the solubility parameters of the liquids. The results show that, in general, henequen cellulosic fibers have properties that are in close agreement with those found in other cellulosic materials from natural sources.